Planar or quasi-planar octa- and ennea-coordinate aluminum and gallium in boron rings

An ab initio theoretical investigation has been performed on planar or quasi-planar octa- and ennea-coordinate Al and Ga centered in X@B-8 (-) and X@B-9 (X=Al, Ga). These high symmetry molecular wheels all turned out to be true minima of the systems and sigma+pi double aromatic in nature, similar to the previously characterized D-8h B@B-8 (-) both electronically and geometrically. Adiabatic and vertical detachment energies of the anions and the ionization potentials of the neutrals have been calculated to aid their eventual experimental identification.